Method and apparatus for overcoming reluctance in material which is in process of magnetic separation and concentration



1958 R. H. STEARNS ETAL 2,362,619

METHOD AND APPARATUS FOR OVERCOMING RELUCTANCE IN MATERIAL WHICH IS IN PROCESS OF MAGNETIC SEPARATION AND CONCENTRATION Filed July 8, 1954 3nventors Fain/E44 H, 57-542! H5204 0 w. Buus attorneys Stats METHGD AND APPARATEE FOR @VERCQMENG RELUCTANCE IN MATERIAL WHICH l3 EN PROCESS OF MAGNETIC EPARATHGN AND CON CEN TRATEIQN Roswell H. Stearns, Wanwalosa, and Harold W. Buns, Milwaukee, Wis, assignors, by direct and mesne ments, to The Indiana dtcel Products Company, Vaiparaiso, Ind, a corporation of Indiana Application July 8, 11954, erial No. 442,058

18 Claims. (Cl. 2ti9-216) tinuation-in-part of our application Serial No. 192,726

filed October 28, 1950 (now abandoned).

In the device shown in the above-identified patent, we employed a magnetic field which was concentrated in its intensity by bringing to an apex a magnetic pole confronting a roll over which was flowing the material to be separated or concentrated. The success of such fiux concentration was limited by the fact that the metal of the pole apex could not handle a greater amount of flux than would saturate the very limited cross section of the pole at the apex. The present invention is based in part on concentration of flux at the base of the roll by the provision of shallow peripheral teeth but principally involves an arrangement whereby the finely divided mate rial upon which the separator or concentrator acts is first allowed to dwell in close proximity to the energized pole, to become magnetized thereby, and is then caused to fiow as close to the peripherally toothed roll as the size of the work particles permits.

In the drawings:

Fig. 1 is a view in vertical axial section diagrammatically illustrating an embodiment of the present invention.

Fig. 2 is a plan view of the intermediate roll of the device shown in Fig. 1 and the underlying chute, portions of the frame and baflies being shown in section.

Fig. 3 is an enlarged fragmentary detail view of the preferred construction of a roll used in the device of the present invention. p Fig. 4 is a view similar to Fig. 3 showing a slightly modified embodiment of the roll.

Fig. 5 is an enlarged fragmentary detail view similar to aportion of Fig. l and showing the baffle 45 adjusted outwardly to a typical position of, use.

The general organization of the device is quite similar to that shownsin the patent. There is a base at 5 which supports the upper and lower pole pieces 6 and 7 and the intervenin ener izin electro-ma netic windin or windings 8.

The hollow and usually rectangular field core 9 has appropriate bearing blocks bolted to it as shown for the rotatable support of the upper and lower armature rolls 10 and 11. Bolt or bolts 12 screwed into the field core at its lower end carry nuts 13, 14 engaging the car 15 on base 5 to. fix adjustably the position of the lower end .of the field core. Secured to the top of the field core is a frame .16 which carries bearing blocks for the rotatable support of another separating roll l7 which, having no field core, is activated almost I entirely by leakage currents from the magnet and effects preliminary separation in a manner hereinafterto be described.

It will be observed that the several rolls lit, 11 and 1 7 desirably rotate on axes which are substantially in tit:

the planes of the top surfaces of the respective poles of 2 the magnet and toward which the ends of the respective poles are bevelled.

The frame 16 constitutes a rigid unit'with the field core 9 and is adjustably connected by bolts 18 with the ear 19 which is engaged by nuts 20 and 21 on the bolts 18 to fix the position of the upper end of the assembly of field core and frame. The ear 19 is mounted on the polar extension arm 22' which is disposed on top of the upper pole piece 6, where it is preferably adjustable upon the key 23, being heldin adjustment by a bolt 24 upon which nuts 25, 26 engage the car 27 fixed to the upper pole piece 6:

The frame 16 not only carries the upper roll 17, but also desirably supports the hopper 30 within which'I preferably employ a feed roll 29 having its surface longitudinally milled as shown at 28 to provide elongated pockets which receive the finely ground material to be separated or concentrated, and deliver such material i small increments from the hopper.

The assembly of frame 16 and field core 9 also carries end and front and back wall portions of a chute organization for confining the material as it is fed past the magnets. The general arrangement being described in the former patent above identified, it will only be briefly mentioned here as comprising, between each pair of rolls, a front wall 31, rear wall 32, and end walls 33. From points between the upper and lower rolls of the respective pairs, the delivery chutes 35, 36 lead outwardly, the latter extending through the rectangular field frame 9. The upper ends of the respective chutes are mounted on cross rods 37 and 38, over which they are hooked. Immediately above each chute is a work deflectinggate 39, at), the gates being respectively oscillatable on the rock shafts e1, 42 to guide to the respective chutes material which is more or less magnetically responsive, according to the setting of the gate.

The ends of the several magnetic poles are relatively blunt. While each is bevelled, it will be noticed that each 'ends in a relatively flat terminal portion. Across this portion extends a relatively non-magnetic. baflie, the several bafiles referred to being designated respectively by reference characters 44, 45 and 46. Each of these is provided immediately above its associated pole with. an

offset shelf portion such as is indicated at 47.

These baflles may be, and desirably are, mounted on rock shafts for their oscillatory adjustment, the rock shafts of bafiles 44, 45 and 46 being respectively designated by reference characters 48, 49 and 50. Even in the most retractedpositions of these baffles, wherein the baffles abut the ends of their respective poles, the lower end of the baffle will lap the rear walls of the chutes to assure that the material traversing the device will remain confined in the chute structure. However, each .bafile may be adjusted toward the associated peripherally grooved roll, it being desirable that the bafile be set to bring the material as close to the teeth of the roll as is practicable to provide sufficient clearance for the free movement of the work. Fig. 5 shows a typical position to which the bafiles may be adjusted in use. It will be observed that its shelf portion 47 remains in close proximity to' the magnetic polar member 6 while the lower end of the baffle extends past the teeth dl'of roll 64 in relatively close proximity to the teeth.

Opposed to the bafiles 44, 4'5, 46 are hopper baffles 51, 52 and 53 respectively, baffles 52 and 53 being rearward extensions, of the front walls 31 of the chute structure. The bafiles 51, 52 and 53 direct onto the shoulders 47 the granular material traversing the apparatus so that such material will dwell within the field where the flux is most intense and will not fall freely between the poles and the classifying rolls 17, 10 and 11. To further retard the otherwise free flow of .the material, I may also 3 employ wedge-shaped deflectors 54, 55 which change the direction of flow, thereby retarding flow.

Below the roll 11, there is a further gate 56 similar to the gates 39 and 40 above described, this being mounted on rock shaft 57 to control the discharge flow as between the delivery spout 58 and the delivery chute 59. It will be apparent that the material discharged from spout 35 will be the most highly magnetic, the material discharged from spout 36 and spout 58 being of progressively de creased magnetic response, and the material discharged from spout 59 being nearly or completely non-magnetic.

One feature of the invention consists in the formation of all of the rolls to provide peripheral teeth which desirably extend circumferentially. Fig. 3 shows a preferred construction of the roll 10, the roll comprising a tube or sleeve 60 having its external periphery helically cut with one or more continuous and relatively fine threads 61. The sleeve 60 is mounted on the shoulders 62 of the heads 63 which are positioned on shaft 64 by the nuts 65 screw threaded to the shaft.

Two changes are suggested by Fig. 4. In the first place, the teeth 610, instead of being helical, are simply formed by peripheral grooves, each of which is normal to the axis of the roll, so that each tooth is annular. In the second place, the roll 600 shown in Fig. 4 comprises a solid annulus mounted directly on shaft 64 instead of comprising a sleeve, as in Fig. 3. There is no necessary connection between the type of teeth shown in Fig. 4 and the type of roll shown in Fig. 4, it being understood that either a solid roll or a sleeve may be provided either with helical teeth as shown at 61, or with annular teeth such as those shown at 610. All of the rolls shown in Fig. 1 are of the solid construction.

It is particularly to be observed that each tooth is shallow and triangular in cross sectional outline so that it presents a relatively sharp apex toward the associated opposing pole of the magnet. Due to the factthat the respective poles, particularly the poles 6 and 7, receive a relatively heavy flux from the electromagnetic windings 8, and are adapted to handle a heavy flux flow before saturation is reached, and since the respective rolls and the field core 9 provide a nearly closed flux path between the poles .6 and 7 (these being of opposite polarity), the magnetic flow through the rolls is very heavy. Nevertheless, at a very large number of points transversely of the apparatus, such flow tends to be concentrated by the apices presented by the tooth or teeth 61 or 610, thereby achieving a very high and effective degree of separation between non-magnetic materials and materials only slightly magnetic.

The effectiveness of separation is attributable in part to the disposition of the sharp edges upon a roll in opposition to the magnet poles, and in part to the fact that the side surfaces of the teeth of the rolls greatly increase the amount of surface which is exposed to the material in the width of the machine. In other words, the convolutions provided by the teeth afford much more magnetic surface in the path of the most intense magnetic flow than would be provided by any smooth surface. In addition, the fact that the rolls are rotating seems to be important tothe result. The rotation of all of the rolls shown is clockwise, and the chains, belts, or other drive connections for effecting such rotation are omitted from the present drawing, these having been illustrated in my former patent and being, in any event, well-known to the art.

More particularly, however, the effectiveness of separation is attributable to the arrangement whereby the successive baffles and deflectors of the chute structure retard the gravity flow of the material, and the respective shoulder portions 47 of the several adjustable baffles 44, 45 and 46 tend to cause the material to dwell at points where it will derive, to a maximum degree, the polarity of the associated pole. The pole 6 and the polar extension 22 of the induced magnet will be of one polarity,

and the associated separator rolls 10 and 17 will be of relatively opposite polarity. Much of the material upon which such a separator or concentrator is required to act will display considerable reluctance. By causing such material to dwell in close proximity to the tip of polar extension 22 and in close proximity to the nose of pole 6 and then passing it into close proximity to the associated separator roll of opposite polarity, the effectiveness of separation is greatly enhanced.

The polarity of pole 7 is, of course, opposite to that of pole 6, but the principle of separation remains the same. The material dwells on the shelf 47 adjacent the nose of pole 7 sufficiently long to break down its reluctance and allow it to acquire the polarity of the pole 7. Thereupon, as it passes in close proximity to the roll 11 of opposite polarity, a very effective separation is achieved.

In operation, the finely divided material introduced into the hopper 3G is carried over the top of roll 29 in the course of the rotation of such roll and discharged onto the inclined baffie 51 whereby such material is guided onto the shoulder 47 of bafile 44, where it becomes materially magnetized. The material accumulating on the shoulder spills over to flow between the stationary pole extension 22 and the teeth of the opposite magnetized rotating roll 17. Although the frame 16 does not provide any such flux path as the field frame 9, there will nevertheless be a tendency for the more strongly magnetic portions of the finely divided material to flow to the left of the dividing gate 39 and be discharged by chute 35. The less strongly magnetic material will pass downwardly through the chute structure, retarded by the inclined surfaces at 54 and 52, to encounter the shoulder 47 of baffle 45. Again the material will become magnetized by the magnetic pole 6, as above described. Fi-

' nally the material accumulated upon the shoulder will spill over between the upper pole 6 of the magnet and the teeth of the opposing roll 10. Here, the flux is highly concentrated and of greater density and consequently a higher degree of separation of the magnetic material will occur, the effected magnetic material being held to the roll to pass to the left of the dividing gate 40 for discharge on chute 36, and the less magnetic material flowing to the right of gate 40 for a further separating action between the lower pole 7 and its opposed complementary roll 11. The operation here is essentially the same as above described except that the flux is of greater density and more highly concentrated and due to the fact that the particles of the finely divided material will have shifted their positions, it will therefore be possible for the roll 11 to deflect to the left of gate 56 additional magnetic material which escaped separation in the operations above described.

It must be understood that the device is not limited to three separating zones as shown in Fig. l, as if, and when necessary, additional fields of definitely increasing magnetic flux density suitable for a higher degree of magnetic concentration or separation may be added, and comprise the device within the meaning of the descriptive matter and claims.

The improved device as herein disclosed is capable of operating with the utmost effectiveness and at relatively high speed upon materials so weakly magnetic that it has heretofore been Very diflicult to achieve any comparable degree of separation.

l. A method of magnetic separation which includes passing particles of magnetic and non-magnetic material by gravity through the gap between poles of differing polarity while guiding such particles upon a circuitous path to obstruct their freedom of movement, causing the particles to dwell slightly and accumulate at one side of the gap in proximity to the region of greatest flux density of one of said poles to overcome the magnetic reluctance of the magnetic material and subsequently passing all such particles at least partially across said gapto dispose them close to another pole of diflering polarity to separate the previously magnetized material from the non-magnetized material and effecting separation between particles acted upon to a greater and lesser degree by said other pole. I

2. The method recited in claim 1 in which the material has been caused to dwell in proximity to the pole first mentioned is physically guided while moving toward said other pole in a direction having a substantial horizontal component.

3. The method recited in claim 1 in which the surface of the last mentioned pole is moved in the general direction of gravity movement of the material acted on thereby.

4. In a magnetic separator, the combintaion with a relatively fixed magnetic pole and an opposed rotatably mounted polar cylinder of opposed, polarity with respect to the fixed pole, there being a gap between said poles, of a chute organization for guiding between said pole and cylinder material requiring magnetic separation, said chute organization including a baffle having a shouldered portion extending along the top of the fixed pole to maintain such material in proximity to the fixed pole for a period of dwell suflicient to overcome its magnetic reluctance and to impart substantially to such material the polarity of the fixed pole, said baffle having another portion extending from the shoulder across the face of the pole and laterally outwardly from the fixed pole and downwardly toward and past the cylinder, said other bafile portion spanning to a substantial extent the gap between the fixed pole and cylinder, whereby material having in substantial part magnetism of the polarity of the fixed pole is carried away from the fixed pole and exposed to the magnetism of opposite polarity of the polar cylinder.

5. The device of claim 4 in which said cylinder is rotatably mounted and peripherally ribbed and grooved.

6. The device of claim 4 in which said baifle has a pivotal mounting above the level of the pole and is provided with a free end portion movable about said mounting between the end of the pole and the face of the cylinder.

7. A magnetic separator comprising the combination with a blunt polarized pole and a non-magnetic baflie extending across the pole, of an armature roll of opposed polarity confronting the pole and provided in a generally circumferential direction with tooth means having sharp apices and intervening grooves over' substantially the entire effective surface of the roll, said blunt pole and sharp roll teeth comprising means for establishing a flux pattern therebetween which is concentrated near the roll and relatively dispersed near the pole, said baflle having a shoulder immediately above the pole, in further combination with means for flowing onto said shoulder material to be separated mechanically, for the momentary dwell of said material and overflow of such material from the shoulder through the space between the pole and the armature roll, said baflle having a portion offset from the shoulder toward the roll across the gap between the roll and pole whereby material subjected during its dwell to the magnetism of the pole is directed into the zone of flux concentration near the roll teeth for exposure to the magnetism of opposed polarity of the roll.

8. The device of claim 7 in which the respective apices and grooves on the roll are helical.

9. The device of claim 7 in which the respective apices and grooves on the roll are annular.

10. A magnetic separator comprising the combination with a pole having a relatively broad vertical end face and a horizontal top surface joined at an angle and an armature member spaced from the'pole and having a face provided with grooves and intervening teeth extending in the general direction of flow of the material, a nonmagnetic bafiie extending across the pole end face, said baflie having a shoulder immediately above the pole and extending generally horizontally along'the top surface thereof and an adjustable support upon which the baffle is movable respecting the pole and means for flowing onto said shoulder material to be separated magnetically for the overflow of such material from the shoulder through the space between the pole and the armature on a path defined by the adjustment of said support.

11. The device of claim 10 in which said means for flowing material onto said shoulder comprises a deflector plate separate from said baffie above said shoulder to slow the flow of material fed by gravity to said deflector .and to change the orientation of said material in the course of its passage to said shoulder.

12. The device of claim 10 wherein said separator further comprises ahopper below said pole and armature, said hopper having a Wall adjacent the pole and lapped by said adjustablebaflle in the position of the baffle, providing the greatest opening between the pole and armature.

13. The device of claim 10 wherein the respective grooves and teeth on the armature member are helical.

14. In a magnetic separator, the combination with an electromagnet comprising an upright core and a coil thereon, of polar plates with substantially horizontal upper and lower surfaces to which the core is substantially normal and which project laterally beyond the coil, lateral substantially flat polar faces adjacent the substantially horizontal upper surfaces of the respective plates and toward whichthe plates are bevelled from their respective substantially horizontal lower surfaces, peripherally shallowly. grooved magnetic rolls mounted for rotation on generally horizontal axes substantially at the level of the substantially horizontal upper surfaces first mentioned and to which said polar faces are adjacent, said rolls having sharply ridged peripheral teeth spaced from said polar faces, a magnetic armature frame having broad portions immediately adjacent the rolls and opposite said polar faces to provide a flux path between the rolls and in a substantially closed circuit withsaid core, in which circuit the spaces between the roll teeth and the polar faces provide the principal gaps whereby the roll teeth and polar faces are of opposed polarity, said flat polar faces and sharp roll teeth comprising means for establishing flux patterns therebetween which are highly concentrated near the roll teeth and relatively dispersed near the polar faces, and non-magnetic baffles disposed between the respective polar faces and roll teeth, said baflies having first portions adjacent the polar faces and onto which material to be separated is deposited for exposure to the polarity of the polar faces, second portions relatively adjacent the roll teeth to expose the material to high concentration of flux near the roll teeth of opposed polarity, and intermediate portions connecting said portions to convey material across said gaps from said first portions to said second portions.

15. The device of claim 14 in which the baflie is provided with a mounting on which the position of its second portion with respect to the roll teeth is relatively adjustable whereby the degree of exposure of the material to the highly concentrated flux near the roll teeth may be predetermined by said adjustment.

16. In a magnetic separator, the combination with first and second poles horizontally spaced to provide a gap therebetween, of chute means for the gravity delivery toward said gap of differential magnetic material requiring separation, a baflle onto which said chute means delivers such material, the baffle partially overlying the first pole and extending thence downwardly and outwardly across said gap toward a lower part of the second pole and terminating in closer proximity to said second pole than to said first pole for discharge of material within the magnetic influence of the second pole, the magnetic reluctance of such material being at least partially overcome in traversing the bafiie portion overlying the first pole, whereby substantial portions of the material ac- '7 quire the polarity of the first pole, thereby enhancing the attraction of the second pole vfor such portions.

17. In a magnetic separator, the combination with first and second poles horizontally spaced to provide a gap therebetween, of means for the gravity delivery toward said gap of differential magnetic material requiring separation, means onto which said gravity delivery means delivers such material, said last-mentioned means comprising a first surface portion disposed in closer proximity to said first pole than to said second pole and having an angle of inclination with respect to the horizontal to tend to accumulate material adjacent and closer to a region of high flux density of the first pole than to the second pole after which the material spills over and flows toward said second pole and comprising a second surface portion extending from said first surface portion across said gap and terminating in closer relation to said second pole than to said first pole to tend to guide material spilling over from said first surface portion across said gap and into proximity to said second pole, the material being retained in the region of high flux density of said first pole for a sufficient time period to at least partially overcome the magnetic reluctance thereof, whereby substantial portions of the material acquire the polarity of the first pole, thereby enhancing the attraction of the second pole for such portions.

18. A method of magnetic separation which includes passing particles of magnetic and non-magnetic material toward a first pole at a relatively rapid rate in a dry flow- 8 able condition, causing the particles to accumulate and remain for a substantial time period in proximity to the region of high flux concentration of the first pole in comparison to the rate of approach of said material to said first pole, retaining material in the region of high flux concentration of the first pole for the time period sufiicient for substantial portions of the material to acquire the polarity of the first pole, and subsequently passing all such particles at least partially across a non-magnetic gap to dispose the particles close to another pole of different polarity to separate the previously magnetized material from the non-magnetized material, and effecting separation between particles acted upon to a greater and lesser degree by said other pole.

References Cited in the file of this patent UNITED STATES PATENTS 4 7,073 Lovett -e Nov. 29, 1892 791,494 Payne Tune 6, 1905 332,322 Wait s Oct. 9, 1905 944,699 Snyder Dec. 28, 1909 1,114,071 Ullrich Oct. 20, 1914 1,965,441 Tyden July 3, 1934 1,967,723 Pehrson et a1. July 24, 1934 2,078,513 Stearns Apr. 27, 1937 FOREIGN PATENTS 103,310 Austria Dec. 15, 19 25 

